Bidimensional sorting in preschoolers with an instrumental learning task

74 lower- and middle-class children aged 2 1/2, 3 1/2, and 4 1/2 years who were successful at unidimensional sorting of 2 objects by either color or form were given feedback for correct bidimensional sorting of 3 objects, 2 of which had been used in unidimensional testing. Four of the 10 2 1/2-year-olds and 58 of the 64 3 1/2- and 4 1/2-year-olds reached criterion on the bidimensional sorting task. Neither social class nor performance on a verbal comprehension test (the Peabody Picture Vocabulary Test) was significantly correlated with success on either unidimensional or bidimensional sorting, although social class and test scores were significantly correlated. The results indicate that Piagetian centration (i.e., the inability to transcend unidimensional attention) is a task- or situation-specific phenomenon, and biodimensional responding is the rule rather than the exception for 3 1/2- and 4 1/2-year-olds in an instrumental situation involving a limited number of stimuli.